how many ounces (oz) there are in a gallon of water depends on where in the world you are. You see, the US liquid gallon measures less (3.785 liters) than the UK imperial gallon (4.546 litres). You should probably bear this in mind when thinking about daily water intake because there’s a big difference between the two (you could be drinking 3/4 of a litre more water if you use the UK imperial gallon conversion). If you want the conversion in cups, by the way, do take a look at this post on gallons and cups.
When converting to ounces (fluid ounces), you need to bear in mind that the US fluid ounce measures more than the UK imperial fluid ounce. The US fluid ounce measures 29.5735mL . By comparison, the UK (imperial) fluid ounce measures 28.4131mL. To assist you, I’ve included the two conversions of gallons to ounces below.
I’ve included two table of conversions to help you see how many fluid ounces there are in a gallon – one using US and one using UK measurements. For converting a specific number of gallons to ounces, use our converter tool.